Regulated hydro-pneumatic strut

ABSTRACT

A level regulated hydropneumatic strut or like component in which a piston-cylinder assembly and a hydroreservoir or accumulator connected to the piston space is so constructed and arranged that the flow paths between the piston space, the annular space or the space surrounding the piston rod and the reservoir are throttled increasingly, viewed from the level position, upon elastic deflections of the piston as a function of the movement path of the piston.

United States Patent [72] Inventor Johannes Ortheil 2,332,520 lO/l943Lucht 1 188/96.9 Anrath, Germany 3,461 ,991 8/1969 Arendarski 188/88(.509) 1 pp No 818,345 FOREIGN PATENTS 817,090 11/1951 Germany 188/88.509 paemed 943 294 l2/l963 Great Britain 267/CH [73] Assignee Langen &Company Dusseldorf, Germany Primary Examiner-George E. A. Halvosa [32]Priority May 17, 1968 Altorney-Holman & Stern [33] Germany [3|]P1750610.4

[54] REGULATED HYDRO-PNEUMATIC STRUT 4 Claims, 1 Drawing Fig.

[52] US. Cl i. 188/289,

I 267/8 Av 267/1316" 1 ABSTRACT: A level regulated hydropneumatic strutor like [51] Int. Cl Fl6f 9/24 component in which a pistomcylinderassembly and a [50] Field of Search ..188/88.509, hydroreservoir oraccumumor connected to the piston Space 96-9; 267/8 A, l is soconstructed and arranged that the flow paths between the piston space,the annular space or the space surrounding the [56] References cuedpiston rod and the reservoir are throttled increasingly, viewed UNITEDSTATES PATENTS from the level position, upon elastic deflections of thepiston 713,691 1 1/1902 Schneider et a1. 188/969 as a function of themovement path of the piston.

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REGULATED HYDRO-PNEUMATIC STRUT BACKGROUND OF THE INVENTION It isalready known in the prior art to provide a strut and attention isinvited to German Pat. No. 1,058,854 in which the stroke of a plungertype piston is damped upon retraction as a function of the path ofmovement, and the damping is accomplished by bores offset axially in thewall of the cylinder with the bores being closed by the pistons, byvirtue of which the effective cross section of the flow is reduced. Thisparticular structural design is disadvantageous in that the dampingincreases only stepwise, and in addition, it is necessary to provide theouter circumference or perimeter, of the cylinder or the cylinder wallwith conduction means for the onward conduction or leading of the fluidwhich has flowed through the bores. Of course, this increases the spacerequirement for mounting in a particularly undesirable manner and afurther disadvantage is that the damping dependent upon the path, viewedfrom the level position, is effective only in one direction.

SUMMARY OF THE PRESENT INVENTION It is an object of this invention toovercome the above and other disadvantages existing in the prior art andto provide a strut of the type under consideration which, without anincreased space requirement, possesses a damping characteristic whichincreases continuously to both sides viewed from the level position.

The present invention solves the problem in that the piston rod isprovided with an axially extending bore in which plunges or moves in asealing manner a tube attached to the housing of the cylinder with thetube tapering from both ends thereof towards its center portion overpart of its length and presenting at the point of least diametertransverse bores which communicate with the interior of the tube whichfunctions as a connection with the hydroreservoir or accumulator, thetransverse bores lying, in the level position of the piston, in the areabetween the piston surface and a transverse bore connecting the annularspace or space surrounding the piston rod with the bore in the pistonrod.

In a particularly efficacious embodiment of the invention, the tube may,for the purpose providing a level control device lying within thehousing of the cylinder, be movable within the housing between two stopsor abutments and may, at that point, in combination with bores and/orannular grooves in the housing, be so designed that the results theoperation of a three 3-way level control valve centered by twooppositely operative springs in the level position of the piston in itsblocking position, with the tube being braced via one spring against thehousing of the cylinder and via the other spring against the closed endof the piston rod.

Further object and advantages of the invention will become more readilyapparent to persons skilled in the art from the following detaileddescription and annexed drawing:

DETAILED DESCRIPTION OF THE DRAWINGS The sole FIGURE is a fragmentaryview in axial cross section of a strut embodying the present inventionwith the strut being illustrated in its level position.

DETAILED DESCRIPTION OF THE INVENTION As shown in the drawings there isprovided a cylinder housing 2'provided with an axially extending bore 1and a slidably mounted piston 3 having a hollow piston rod 4. The pistonrod 4 is provided with an axial bore 5 into which a tube denotedgenerally 6 is adapted to plunge or move. The tube 6 is addi- It willfurther be noted that the tube 6 is formed with an annular groove 10with the groove 10 cooperating with corresponding axially spaced annulargrooves 11, I2 and 13 in the housing 2 to constitute a three 3-way levelcontrol valve means.

It will be noted that the upper end of the bore 7 of housing 2 isprovided with an internal thread for receiving an external threadprovided on a neck portion of a hydroreservoir or accumulator 14. A coilspring 15 is biased between the end of the neck portion of the reservoir14 and the upper surface of the collar or shoulder 8.

The tube 6 is formed with a through bore 16 and the perimeter or outersurface of the tube 6 includes two cylindrical portions 1781.18respectively and from which portions the tube tapers towards its centerarea. At the point of smallest diameter, the tube 6 is provided with atransverse bore 19 and in the level position of the piston 3, the bore19 lies approximately in the zone between piston face 21 directedtowards piston space and a transverse bore 22 formed in the piston rod 4adjacent the piston 3. The bore 22 provides communication between anannular space 23 or the space surrounding the piston rod 4 and the bore5 within the piston rod. A packing 24 seals the annular space 23 fromthe surrounding atmosphere.

A coil spring 25 positioned within the bore 5 is biased between theclosed end of the piston rod 4 and the lower end of the tube 6. A checkvalve 26 such as a spring loaded ball allows the unhindered return flowfrom the reservoir 14 into the piston space 20.

While the operation of the invention is believed to be apparent from theforegoing description, it may be summarized as follows:

In the position illustrated, the piston 3 is in its level position andthe springs 15 and 25 acting on the opposite ends of the tube 6 are inequilibrium and are so correlated that the tube 6 occupies a location inwhich the annular groove 12 connected by way of connection A with thepiston space 20 is separated from both the annular groove 11 connectedwith a pressure connection P as well as from the annular groove 13connected with a tank connection or drain T.

The transverse bore 19 is present in the area between the piston face 21and the transverse bore 22 so that the full cross section from thepiston zone 20 or from the annular space 23 to the transverse bore 19,respectively has its maximum value. Upon the inward movement of thepiston 3 caused, for example, by an irregularity existing in the roadsurface, initially liquid is displaced substantially unthrottled fromthe piston space 20 via the bore 5 and transverse bore 22 into theannular space 23 or via the bore 5, bore 19, bore 16 and bore 17 intothe reservoir or accumulator, respectively. At increasing stroke, due tothe coincity of the tube 6, the gap or hiatus between the outer surfaceof the tube 6 and the piston 3 becomes smaller and as a consequence, theresistence to flow becomes greater. When the piston 3 approaches thecylindrical portion 17 of the tube 6 and finally reaches such portion,the flow resistance is so great that it must be equated with a hydraulicabutment. Simultaneously with this process, the spring 25 is subjectedto more compression and due to this action, the force of the spring 25increases beyond the force of the spring 15 whereby the tube 6 isdisplaced accordingly.-

The annular groove 10 in the tube 6 connects the annular groove 12 withthe annular groove 11 and hence the pressure connection P with thepiston space. Under static load variations, for example, due to added orincreased loading, the liquid then flows into the piston space 20 untilthe piston 3 has again attained its level position. By a proper designof the annular grooves 10-13 it is possible to achieve that under staticload variations, the level regulation is effected whereas at rapiddynamic load variations, the level regulation does not become operative.

The spring movements in the piston 3 which exceed the possible stroke ofthe tube 6 are absorbed by the spring 25 and during a subsequent outwardmovement, initially liquid is displaced from the reservoir 14 or fromthe annular space 23 into the piston space 20 at decreasing damping,respectively. After the level position has been passed, the dampingagain increases due to the fact that the gap or hiatus between the bore22 and the tube 6 becomes increasingly smaller with further elasticextension. The resistance to flow between the annular space 23 and thepiston space 20 increases accordingly and when finally the transversebore 22 is closed by the cylindrical portion 18, there again results thehydraulic abutment herein above described.

Upon elastic tension beyond the level position, the force of the springpredominates over the force of the spring 25 and the tube 6 is sodisplaced that the annular grooves 12 and 13 are connected by means ofthe annular groove 10. If the elastic tension is effected statically,the liquid flows until the piston 3 has again reached its levelposition. Dynamic tensions have, as has been explained practically noeffect.

At variance with the embodiment illustrated in the drawing, it is, ofcourse, possible to vary or alter the coincity of the tube 6, Forexample, it may be desirable to damp movements in the vicinity of thelevel position, not as a function of the movement path. In thissituation, the tube 6 may be provided approximately in its center zonewith a cylindrical portion which in this area causes no, or at least aconstant, damping.

Moreover, it is possible to provide between the reservoir or accumulator14 and the bore 7 for the development of the basic dampening, adouble-acting throttle valve known per se. Finally, it is clear that theannular grooves ll, 12, and I3 serving as level control valve means inconnection with annular groove 10 of tube 6 may be differently arrangedor replaced by bores so long as the desired three 3-way operation ismaintained or preserved.

The taper may, as illustrated, be conical or it may be designed inanother suitable form. When the piston movement is strongly damped, itis advantageous to install one or more valves 26 since the return timeof piston 19 to its level position can then be shortened. Naturally, thetype and installation of the check valve 26 are elective in accordancewith the problems to be solved.

lclaim:

l. A level-regulated hydropneumatic strut including a cylinder having ahousing, a piston and piston rod within the housing dividing theinterior thereof into a piston space and an annular space, respectively,a hydroreservoir connected to the interior of the housing, and means forproviding communication between the piston space, the annular space andthe hydroreservoir being increasingly throttled, viewed from the levelposition of the piston upon elastic deflection of the piston dependentupon the path of the piston, the improvement being said piston rodhaving an axially extending bore, a tube attached to the cylinderhousing extending through the piston into the bore of the piston rod ina sealing manner, said tube having its outer periphery tapering overpart ofits length at both ends toward the center thereof, said tube, atits area of smallest diameter being provided with a transverse bore,said piston rod having a transverse bore for connecting the annularspace with the axial bore of the piston rod, the transverse bore of saidtube lying, in the level position of the piston in the area between thesurface of the piston facing the piston space and the transverse bore inthe piston rod, first spring means biased between the cylinder housingat one end of the tube, second spring means biased between the other endof the tube and the piston rod, said cylinder housing having two axiallyspaced abutments between which said tube is movable, a pressureconnection, a drain connection, said cylinder housing in the area ofsaid abutments having a plurality of communication means adapted tocommunicate with the pressure connection, the drain connection, and thepiston space respectively, and said tube having communication means forcoacting with the communication means of the cylinder housing wherebyproviding a three 3-way level control valve which is centered by saidfirst and second spring means at the level position of the piston, thecommunication means providing communication between the ressure anddrain connections respectively being separated rom the communicationmeans connected with the piston space.

2. The level-regulated hydropneumatic strut as claimed in claim 1further including a check valve within the cylinder housing between thepiston space and the reservoir with the check valve opening in adirection of the piston space.

3. The level-regulated hydropneumatic strut as claimed in claim 1 inwhich said tube is provided with two cylindrical portion having an outerdiameter corresponding to the inner diameter of the bore of the pistonrod, with the cylindrical portion in the piston space, during theinwards stroke of the piston, interrupting the flow path between thepiston space and the annular space or the reservoir respectively whileduring the outward stroke of the piston, the other cylindrical por tioncovers the transverse bore in the piston rod whereby hydraulic abutmentsare developed upon exceeding maximum stroke of the piston.

4. The level-regulated hydropneumatic as claimed in claim 2 in which thetapers of the tube are conical.

1. A level-regulated hydropneumatic strut including a cylinder having ahousing, a piston and piston rod within the housing dividing theinterior thereof into a piston space and an annular space, respectively,a hydroreservoir connected to the interior of the housing, and means forproviding communication between the piston space, the annular space andthe hydroreservoir being increasingly throttled, viewed from the levelposition of the piston upon elastic deflection of the piston dependentupon the path of the piston, the improvement being said piston rodhaving an axially extending bore, a tube attached to the cylinderhousing extending through the piston into the bore of the piston rod ina seaLing manner, said tube having its outer periphery tapering overpart of its length at both ends toward the center thereof, said tube, atits area of smallest diameter being provided with a transverse bore,said piston rod having a transverse bore for connecting the annularspace with the axial bore of the piston rod, the transverse bore of saidtube lying, in the level position of the piston in the area between thesurface of the piston facing the piston space and the transverse bore inthe piston rod, first spring means biased between the cylinder housingat one end of the tube, second spring means biased between the other endof the tube and the piston rod, said cylinder housing having two axiallyspaced abutments between which said tube is movable, a pressureconnection, a drain connection, said cylinder housing in the area ofsaid abutments having a plurality of communication means adapted tocommunicate with the pressure connection, the drain connection, and thepiston space respectively, and said tube having communication means forcoacting with the communication means of the cylinder housing wherebyproviding a three 3-way level control valve which is centered by saidfirst and second spring means at the level position of the piston, thecommunication means providing communication between the pressure anddrain connections respectively being separated from the communicationmeans connected with the piston space.
 2. The level-regulatedhydropneumatic strut as claimed in claim 1 further including a checkvalve within the cylinder housing between the piston space and thereservoir with the check valve opening in a direction of the pistonspace.
 3. The level-regulated hydropneumatic strut as claimed in claim 1in which said tube is provided with two cylindrical portion having anouter diameter corresponding to the inner diameter of the bore of thepiston rod, with the cylindrical portion in the piston space, during theinwards stroke of the piston, interrupting the flow path between thepiston space and the annular space or the reservoir respectively whileduring the outward stroke of the piston, the other cylindrical portioncovers the transverse bore in the piston rod whereby hydraulic abutmentsare developed upon exceeding maximum stroke of the piston.
 4. Thelevel-regulated hydropneumatic as claimed in claim 2 in which the tapersof the tube are conical.